There's no denying that Will Smith and his Focus costar Margot Robbie put their inhibitions aside inside a photo booth recently. Yet an insider insists the images simply show two friends goofing off – and nothing more.

"The photo booth was on set," the source tells PEOPLE. "The whole cast and crew were there and everyone was sharing all the photos being taken. They are just friends and were just being silly."

The black and white photos – which show Smith, 45, and a costumed Robbie, 23, exposing their chests – were published in a tabloid this week as a sign the actor could be cheating on wife Jada Pinkett Smith. (The Australian Robbie, who is single, has been previously linked to Leonardo DiCaprio, her costar in The Wolf of Wall Street.)

"Will and Jada's marriage is fine," says the source. "Everyone there knows it was nothing."

The insider adds that the photo booth was brought on set during a day of shooting to celebrate cast and crew before moving locations. "This was done in front of many people goofing around," the source says. "They are just friends. This was a very fun and friendly set overall."

Rumors about the state of the Smiths relationship have long dogged the couple, and last year Pinkett Smith, 42, brushed them off while speaking to Essence.

"We're not getting a divorce. Where am I gonna go? Where am I going to go?" she said.

In late September, Pinkett Smith posted a Facebook shot of her and her "boo" – along with Smith's older son Trey – in Louisiana, where Smith was filming.

"The handsome two and I about to roll through the beautiful swamps of Louisiana with Willow and Jaden as well:) It was an amazing day, and I feel so lucky to have a beautiful family to have shared it with."